Among my minor academic achievements is a History A level of an undistinguished grade, the fruit of a long and ponderous two-year plough through the 19th century. All I can remember of it were Metternich's machinations at the Congress of Vienna and the Repeal of the Corn Laws. So, I was chuffed to bits when said Corns Laws were mentioned in Leigh's film of the other topic I recall, Peterloo; a massacre after Napoleon surrendered.

The film begins on the battlefield of Waterloo and initially it seems like the film will build its narrative around the journey of two men from Loo to Loo: a shell-shocked infantryman who returns to a Manchester of poverty, starvation and suppressed wages and Lord Byng, Wellington's second in command whose reward is to be given control of The North. But the pair of them soon get lost in the multicharacter sprawl of Leigh's vision, though the contrasting viewpoints of the worker and the gentry remain throughout the film.

Leigh doesn't do costume drama's like anybody else. Granted, Dick Pope's cinematography is magnificent, but not as a set of pretty pictures. A desire for naturalism means that if realism calls for faces to be in shadows, they remain underlit. The ruling classes are a series of grotesque gargoyles (every performer seems to have found some vocal tick, stutter or mumble for their character) but are not caricatures of evil. Their sincerity in the belief that they are doing the best for their country is total. The workers are not the idealised downtrodden, just ordinary people pushed a bit too far and whose leadership are mostly presented as preening windbags.

Any other filmmaker making a film about a massacre of men, women and children would have made an angry, rabble-rousing piece. Leigh's film has fire, but it is too worldy wise to be banging the drum. This is the birth of the Labour movement but there is a detachment in the vision, a resigned sense that things won't be getting better. The film is really good at delineating the political process, revealing how oratory works, how both sides talk themselves into believing that their truth is so strong, it can be pursued at all costs. His approach is honest and defiantly anti-dramatic: a lot of it is people making speeches. It is a fascinating film but, genuinely thought provoking but much like those long hours over the history books, a bit of a slog at times.